JP2006110543A - Method for treating waste water containing high-concentration organic matter and defoaming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a defoaming apparatus in which the securement of a large quantity of dissolved oxygen necessary for activity of a microbe and the prevention of a large quantity of bubbles form being generated by an aerating operation are satisfied at the same time when waste water containing high-concentration organic matter is treated in a short time by an activated sludge method. <P>SOLUTION: A large quantity of dissolved oxygen in water is secured by using a medium-depth aeration tank and/or a high-concentration oxygen aeration tank. A draft tube 2 having an aeration wheel 3 at the bottom is arranged in the centers of one or both of the above-mentioned aeration tanks and the liquid to be treated is circulated by rotating the aeration wheel so that a downward flow is formed on the inside of the draft tube and an upward flow is formed on the outside of the draft tube. A large quantity of bubbles to be generated by the aerating operation are collected in the draft tube and annihilated by the aeration wheel at the bottom of the draft tube. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention increases oxygen transfer efficiency in an aeration treatment tank that treats high-concentration organic wastewater in various industries with sewage, human waste, and various types of industries, and efficiently eliminates a large amount of foam generated during the wastewater treatment. The present invention relates to a high concentration organic waste water treatment device and a defoaming device.

In aerobic aeration treatment with activated sludge of high-concentration organic wastewater such as shochu, it is necessary to supply a large amount of oxygen and eliminate a large amount of bubbles generated by the aeration treatment. In order to increase the efficiency of oxygen supply, a deep aeration tank or a high-concentration oxygen aeration tank is used as a method with high oxygen transfer efficiency. When the amount of aeration is increased to supply oxygen, a large amount of bubbles are generated on the liquid level of the aeration tank due to many substances having surface activity contained in the treated water.
If this bubble overflows from the aeration tank or flows out into the subsequent process, the operation function will be paralyzed, causing serious problems in plant operation, so defoaming is indispensable.
Conventionally, as a method of defoaming, an antifoaming fan, injection of an antifoaming agent, or a combination of an antifoaming fan and an antifoaming agent has been performed. These methods require the monitoring of the generation of foam and the implementation of defoaming work as a result, which makes the on-site management work very complicated, and the costs associated with the application of antifoaming agents are high, and these are expensive operation and maintenance costs. Needed. Furthermore, the addition of antifoaming agent generates BOD (Biochemical Oxygen Demand) derived from it, which degrades the processing efficiency and also adds the third substance, that is, contamination, and restricts the use of processed products. It was.

Thereafter, as an improved type, “a defoaming device for a deep aeration tank that does not require much upper space, reliably collects generated bubbles and efficiently breaks bubbles” (see, for example, Patent Document 1) has been proposed.
In addition, the treatment of sewage using a medium-deep aeration device or a high-concentration oxygen aeration device has a higher high-pressure or partial pressure of oxygen compared to the conventional standard activated sludge aeration tank with a depth of 4 to 5 m. In recent years, it has been proposed that the oxygen transfer efficiency is high, the processing efficiency is very excellent, and the installation area can be saved. (Aeration treatment apparatus with a high-concentration oxygen gas circulation channel) (see, for example, Patent Document 2).

In addition, it is a known technique that a large amount of yeast was continuously produced while defoaming from sulfite pulp waste liquor in the yeast production field of fermentation industry. (For example, see Non-Patent Document 1)
JP-A-9-103607 Japanese Patent Laid-Open No. 5-23689 Microbiology Handbook (Gihodo June 15, 1966) p943 (Waldhof-fermentor) INDUSTRIAL AND ENGINEERING (1951, Vol 43, No8, P1702-1711) Food Yeast From Sulfite Liquor.

Problems of the prior art The method described in Patent Document 1 described above is 1) the defoaming equipment is quite large and the equipment costs are high, and 2) the collection hood covers 80% of the upper surface area of the outer tube, and the aeration tank There are problems such as trouble in maintenance. The method of Patent Document 2 described above is not equipped with a defoaming device. Further, the method of Patent Document 3 has problems such as a shallow aeration tank and poor energy efficiency.

There are enormous amounts of various needs related to the generation and recycling of waste and processing forms such as shochu distillation residue, food processing residue, slurry manure such as livestock, food residue with a lot of moisture, and residue of fruit and vegetables in the field.
Since these have a high moisture content of 90-95%, fossil fuels such as heavy oil are required for incineration, which emits carbon dioxide and goes against the prevention of global warming. Again, wet decomposition with microorganisms is desirable. In other words, it is expected that the future goal will be to grind organic matter, decompose microorganisms, collect the cells, and reuse them as useful sources such as protein sources and organic fertilizers.

Switching to chemical fertilizer and grain feed, which are conventional products in the agricultural field, technical instability and difficulty due to cost increase. Distance and fare between production and consumption. There are a lot of problems. In addition, it is difficult to secure sales destinations for compost and feed, such as the stability of quality, product prices, unestablished use technology, high prices for existing chemical fertilizers and grain feeds, etc. There are many cases.
The conventional simple soil reduction is restricted from the viewpoint of preventing groundwater contamination such as nitrate ions, and the organic waste is expected to be reused as fertilizer and feed by microbial treatment, and the regulation law has already been enacted and enforced. Yes. These are separated into solid and liquid, and the solid content is incinerated, composted, etc., and the liquid content is treated by draining and flowing into the river, or returned to the field. I am very in trouble.

An anaerobic-aerobic high-concentration activated sludge method using high-concentration activated sludge was proposed as an efficient treatment method for high-concentration organic wastewater treatment from the viewpoint of reducing treatment costs. Removal and phosphorus removal are required to be performed at the same time, and some have been implemented.
There is also a demand for a technique for microbial degradation of everything including solids.

Although it has not been solved as a contradictory phenomenon in the past, most of the above problems are solved by reducing the processing cost of high-concentration organic wastewater. And this technology was completed.

That is, as an aeration method for supplying a large amount of oxygen for treating high-concentration organic wastewater by an activated sludge method in a short time and a means for simultaneously satisfying the defoaming of a large amount of bubbles generated by the aeration operation An apparatus and a method for combining a deep layer aeration tank and / or a high concentration oxygen aeration tank and a waldhof-fermentor type defoaming apparatus are provided.

About oxygen supply:
In the deep aeration tank, the depth of the tank is set to 10 m to 150 m, the pressure of air when dissolving oxygen in water is set to 2.0 to 16 times the atmospheric pressure, and the oxygen transfer efficiency is increased. The high-concentration oxygen aeration tank has a depth of 4m to 5m, and the oxygen concentration is increased to 40% to 80% by an oxygen generator to aerate the oxygen partial pressure to 2-4 times that of air. , Increase oxygen transfer efficiency.
Organic wastewater treatment apparatus characterized by increasing oxygen transfer efficiency over a normal aeration tank (aeration of air at a depth of 4 m to 5 m) in combination with any of the above aeration methods and Processing method.
In the high-concentration oxygen aeration layer among the aeration tanks with improved oxygen transfer efficiency, a control device is provided as a safety measure so that the oxygen concentration in the voids in the aeration tank does not exceed 20%.

About foam prevention technology:
The waldhof-fermentor has a draft tube with an aeration wheel attached to the bottom in the center of the aeration tank. By rotating the aeration wheel, the inside of the draft tube is downward and the outside is circulating upward. Let A defoaming device for an aeration tank, wherein bubbles in a liquid are eliminated by an aeration wheel in the middle of a circulating flow.

Air or high-concentration oxygen is supplied into the circulating flow of the liquid to be processed through a hollow spinner disposed on the aeration wheel, and fine bubbles are generated in the liquid to be processed by high-speed rotation of the spinner.
The rotation speed of the aeration wheel is 300 to 400 rpm, and the liquid to be treated is sent from the inner cylinder to the outer cylinder with the same role as the impeller of the centrifugal pump. This process works to eliminate bubbles in the liquid. Furthermore, a swirl flow is generated in the spinner portion protruding outside the wheel end plate. The peripheral speed of the spinner tip is very fast at 19.2 to 35.6 m / sec, forming aerated bubbles and promoting oxygen dissolution in water by vigorous stirring.

The circulating fluid in the upward flow is rotated by the rotation of the aeration wheel outside the draft tube. The bubbles on the liquid level flow from the outside to the inside due to gravity according to the level difference of the liquid level generated by the centrifugal force due to the rotation, and gather in the draft tube beyond the upper edge of the draft tube. A defoaming device that collects all the generated bubbles in a draft tube by the above operation.

  A defoaming apparatus characterized in that bubbles are liquefied and disappear when the liquid and bubbles of the preceding paragraph pass through the aeration wheel as a circulating flow.

In the present invention, in order to achieve the above object, from the oxygen transfer efficiency, the processing efficiency, the installation area of the equipment, etc., using the deep layer aeration method and / or the high concentration oxygen aeration method as the oxygen supply method in water, This is solved by a defoaming device having a configuration comprising a draft tube in the center of the aeration tank and an aeration wheel provided at the bottom of the draft tube. The configuration and role of this defoaming device are as follows.

Occurred during wastewater treatment by placing aeration tubes in the aerating tank and its lower part in an aeration tank with high oxygen dissolution efficiency and dissolved oxygen concentration and / or a high-concentration oxygen aeration tank. It is a defoaming device for an aeration tank excluding foam.

The draft tube with the aeration wheel attached to the bottom is provided at the center of the aeration tank, and the aeration wheel is rotated to generate a circulation flow of the liquid to be treated with the inside of the draft tube facing downward and the outside facing upward. This is a defoaming device for the aeration tank.

This is a defoaming device for an aeration tank that generates fine bubbles of air or high-concentration oxygen in the liquid to be treated by rotation of a spinner disposed on the aeration wheel and rotates the circulating liquid outside the previous draft tube.

According to the level difference of the mortar-like liquid level generated by turning, the liquid and bubbles flow down from the outside toward the inside by gravity, pass over the upper edge of the draft tube, and pass through the aeration wheel via the draft tube. It is a defoaming device for an aeration tank, characterized in that bubbles sometimes liquefy.

Bubbles that floated on the liquid surface, that is, on the water surface of the outer tube water passage (3a), fall into the inner tube by gravity along with the circulating flow along with MLSS (Mixed Liquor Suspended Solid) and aeration. While circulating through the wheel to the outer tube, the foam disappears due to the foam breaking force of the aeration wheel.

As described above, according to the apparatus of the present invention, a sufficient amount of air or high-concentration oxygen is aerated to obtain the necessary oxygen with an apparatus having a simple structure, and the generated bubbles are reliably collected and efficiently collected. By breaking the bubbles, it was possible to realize the condition that the high-concentration organic raw effluent was decomposed with the mandarin orange.

In addition, it is a useful technology for wastewater treatment because there is no application restriction due to contamination of treated products by not adding third substances such as antifoaming agents, and there is no need to monitor foaming and spray antifoaming agents. is there.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side view of an apparatus according to an embodiment of the present invention. 2 is a plan view of the aeration wheel, and FIG. 3 is a cross-sectional view (side view) taken along line II-II in FIG. 1 is an aeration tank body. Reference numeral 2 denotes a draft tube (foam collecting part), the upper end of which is an open end, and the lower end of which is welded a metal plate (end plate) having a hole through which a hollow shaft for ventilation passes. Like the impeller of a volute pump, the metal plate portion and the aeration wheel are combined through a slight gap. This part is 3 in FIG. 1 and is an aeration wheel (defoaming part). 4 is an aeration wheel drive motor. 5 is the overflow pipe. 6 is a ventilation control device. 7 is a hollow shaft for ventilation. 8 is an oxygen generator. 9 is the inlet of the treated water. 3a is a flow path formed between the inner cylinder and the outer cylinder.

As shown in FIG. 2, the aeration wheel has six pipes (spinners) curved outward from the center, and both ends of each spinner are open. The opening at the center is connected to a hollow shaft connected at the center of the aeration wheel, and the other is open to the fermentation liquid at the outer periphery of the aeration wheel.
The aeration gas is discharged into the water as bubbles from the spinner opening at the outer peripheral portion of the aeration wheel through the ventilation shaft and the spinner. Since the opening of the spinner on the outer periphery of the aeration wheel rotates at high speed in water, the generated bubbles become extremely fine and contribute to the improvement of dissolved oxygen concentration in water. Further, the centrifugal force generated by the rotation of the spinner of the aeration wheel (corresponding to the impeller of the spiral pump) causes the liquid in the draft tube to flow from the inner tube toward the outer tube along the spinner.

The operation of the above configuration will be described below. When the inflow from the treated water inlet 9 and the supply of air by the aeration wheel and the circulation of the liquid reach a steady state, the liquid surface of the flow path 3a becomes a mortar shape with a low inside and a high outside, and bubbles on the liquid surface are caused by gravity. It slides down on the surface, falls into the draft with the liquid, and circulates.

In the present invention, the bubbles are reliably collected by dropping the bubbles onto the water surface of the flow path 3a into the draft tube at the center using the rising of the liquid surface due to the swirling flow of the liquid. The collected bubbles are surely eliminated by passing through the aeration wheel.

Further, during this circulation process, the organic matter in the water is rapidly and aerobically decomposed by microorganisms, protozoa, etc. by supplying sufficient oxygen by the medium-deep layer aeration method and / or the aeration method of high concentration oxygen.

Further, the present invention is not limited to the integrated defoaming apparatus shown above, and devices corresponding to aeration, circulation, defoaming, rotation, and the like may be appropriately combined.

Example 1 of the defoaming part of the present invention is described.
Example of operation of Waldhof-fermentor Excerpt from Non-Patent Document 1 See Fig. 1. Air enters from the shaft, its tip is connected to the aeration wheel, and is discharged from the spinner into the liquid. There is a draft tube just above the Aeration wheel, and an overflow pipe is installed slightly higher than the upper side of the draft tube. When air is blown while rotating the shaft, the liquid rises while swirling from the outside and falls toward the inside of the draft tube. Therefore, even if foaming is performed, the foam can be removed mechanically, so that a large amount of air can be passed. The latest type of Mannheim plant has a capacity of 300m ^3, aeration-wheel diameter 1.7 m, spinner is six, which made performed rotation of 400rpm with a motor of 100kw. The yeast is automatically removed from the overflow pipe along with the foam and centrifuged. Fully automatic operation is possible while adding the culture solution.

Example 2
About the structure, dimensions, operating conditions, etc. of the defoaming part of the present invention
Structure and operation of Waldhof-fermentor (Example) Example of yeast production from sulfite waste liquid Fermenter material, shape: material: 304 stainless steel, diameter: 7.93 m, height: 4.27 m, upper end: open port,
Draft tube: Diameter: 1.22m (fixed to the wall of the fermentation tank with a support rod),
Filling amount of liquid to be treated: 90.9m ³ (gas-liquid mixed state 204.6m ³ ), residence time in fermentation tank; about 4 hours Aeration: aeration wheel; 300rpm, 186.5Kw, 48.3m3 / min, no sterilization This type of aeration device does not require an antifoam. Adjust the air flow on the suction side of the blower. Ventilation is measured with an orifice and manometer. Hollow shaft for ventilation: Diameter; 8 inches. Ammonia phosphate and potassium chloride are added as an aqueous solution and added continuously by gravity. 20% ammonia is added continuously according to the sugar content in the raw material. PH: around 5.
A predetermined amount of purified raw materials, inorganic salts, and ammonia are continuously fed from a draft tube having a high mixing speed.
The fermentation temperature is maintained at 37 ° C. Heat exchange is 6800L / min.

Side view of an apparatus according to an embodiment of the present invention. Plan view of the aeration wheel of the present invention II-II sectional view (side view) of Fig. 2

Explanation of symbols

1 Aeration tank body
2 Draft tube
3 Aeration wheel
3a Flow path between draft tube and outer wall of aeration tank
4 Aeration wheel drive motor
5 Overflow pipe
6 Ventilation control device
7 Hollow shaft for ventilation
8 Oxygen generator
9 Untreated water entrance
10 Spinner

Claims (7)

In order to supply a large amount of oxygen in order to process high-concentration organic wastewater in a short time by the activated sludge method, a medium-deep layer aeration tank and / or a high-concentration oxygen aeration tank are used. A waldhof-fermentor-type defoaming device and wastewater treatment method used to eliminate bubbles. In the middle and deep layer aeration tank, the depth of the tank is set to 5 m to 200 m, and the pressure of air at the time of dissolving oxygen in water is set to 1.5 to 20 times the atmospheric pressure to increase the oxygen transfer efficiency. In addition, the high-concentration oxygen aeration tank has a depth of 2 to 30 m, and the oxygen generation device raises the oxygen concentration from the air to increase the oxygen partial pressure by 1.5 to 5 times that of air, thereby advancing oxygen. Increase efficiency.
2. The high concentration according to claim 1, wherein the oxygen transfer efficiency is higher than that of a normal aeration tank (air is aerated in a tank having a depth of 2 to 5 m) by using one or both of the above aeration means. Organic wastewater treatment method. 3. The processing method according to claim 1, wherein the high-concentration oxygen aeration tank is provided with an oxygen detection device that adjusts the air concentration on the liquid level of the aeration tank to 20% or less.   2. The waldhof-fermentor is provided with a draft tube having an aeration wheel attached to the bottom of the aeration tank, and rotates the aeration wheel to generate a circulation flow of the liquid to be treated. Aeration tank defoaming device. 2. The air or high concentration oxygen is supplied into the circulating flow of the liquid to be processed through a hollow spinner in the aeration wheel, and fine bubbles are generated in the liquid to be processed by high-speed rotation of the spinner. Or the processing apparatus of 4. 6. The processing method according to claim 1, wherein the circulating fluid is rotated by rotation of the aeration wheel outside the draft tube, and all generated bubbles are collected in the draft tube by the operation. . 7. The processing method according to claim 6, wherein the bubbles are liquefied and disappear when the liquid and bubbles of the previous item pass through the aeration wheel as a circulating flow.

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